So differences between cohesive and non cohesive soils appear as high versus low plasticity properties with cohesive soils scoring higher. Geotechnical engineers may analyze a soil sample to gauge its plasticity, or how well it molds together. Hence, tensionresistant foundations are required for counter acting the heave problem. Pi properties soil type cohesion 0 non plastic sand non cohesive cohesive 717 medium plasticity silt clay cohesive 17 high plasticity clay cohesive table 2. Investigation on engineering properties of soil mixtures comprising of expansive soils and a cohesive non swelling soil dr.
Performance improvement of flexible pavement on swelling. We provide these services in support of all types of earthwork applications. Soil properties and special geotechnical problems related to stream stabilization projects. That property provides a weak bond among the soil grains to cause cohesion. Soilmixtures comprising of expansive soils and a cohesive nonswelling soil. When added to soils, including those with sandy content, water plays a vital role in soil cohesion because of its surface tension. It is possible to make a vertical cut in silts and clays and it remain standing, unsupported, for some time. Field guide to non cohesive soil density and angle of friction values. Oct 02, 2014 in 1978, mr katti had proposed concept of using cohesive non swelling layer to reduce effect of swelling. Sand cushion method and cohesive non swelling cns layer method are very popular. Characteristics of cohesive soils stabilized by cement kiln dust. Scour in cohesive soils has been a challenge for engineers and designers. In this study clay soil added with microsilica is used to evaluate existing failure criteria for cohesive soil.
Interpretation of rice husk ash on geotechnical properties of. Pdf double layer theory and compressibility of clays. These volume changes can either in the form of swell or in the form shrinkage and this is why they are sometime known as swell shrink soils. What is the difference between cohesive soil and cohesionless soil. Plasticity and compaction characteristics of soil mixtures. How is cohesive non swelling soil mechanics abbreviated. The likely explanation is that there is a relationship between erodibility and soil properties but that this relationship is quite complicated, involves advanced soil properties, and. In order to estimate the transmitted swelling pressure distribution behind a retaining wall, using with interface element, a new finite element model and a code swelpres have been developed. Unlike noncohesive soils, practical measurement techniques and well accepted guidance on the scourability of cohesive soils are severely lacking. This absorption factor increases a soil s capacity to compact into a mold. Dec 20, 2007 transmitted swelling pressures affected by the soil properties of the backfill especially at the interface between the backfill and retaining wall. The composition and proportion of these components greatly in. Fattah abstract cement kiln dust ckd is a waste byproduct from the manufacture process of the cement, which contributes to environmental pollution.
Cohesive soil means clay fine grained soil, or soil with a high clay content, which has cohesive strength. Cohesive nonswelling soil cns cushion technology is widely used to solve swelling deformation. The present trend of replacement has been shifted to cohesive non swelling material. Variable cohesion model for soil shear strength evaluation shahkar shahangian dba engineering limited, toronto, ontario abstract soil cohesion is the result of the reaction of an extremely large and countless number of resisting elements on the failure.
In clay and silts, therefore, some other factor must contribute to shear strength. Bureau of indian standards evolved the guidelines for canals in expansive soils by introducing cohesive non swelling soils cns with a suitable thickness depending up on the swelling characteristics of the expansive soils. Our automated equipment permits us to run any type of consolidation, triaxial, or direct shear test a client specifies. A number in parentheses indicates the year of last reapproval. Paper open access expansive clay soil stabilization using. The non swelling soil was collected from wuhan, hubei province, china. So noncohesive soil environments contain little to no clay or fine particles while cohesive soils contain high amounts of clay and fine particles. Only when the expansive soil shows low to moderate swelling characteristics do sand or sand and boulder cushions perform adequately. They are soils possessing the property of cohesion of varying degree and non expanding type clay minerals such as illite and kaolinite and their combination with low plasticity with liquid limit not exceeding 50percent. Cns is defined as cohesive non swelling soil mechanics rarely.
The body as acted upon by an externally applied stress system, the state of stress on any plane through the body obtained by the clay soil performed in this study. Performance, problems and remedial measures for the. Minerals such as salt and caliche can add to a soil s cohesive properties. Key aspects that need identification when dealing with expansive soils include. Cohesive soil article about cohesive soil by the free. Comprising of expansive soils and a cohesive nonswelling soil. According to katti 1978, with saturation of expansive soil cohesive forces are developed up to a depth of about 1. In a second stage, after desiccation cracks were closed, soil volumetric expansion is only. Isolation of foundation fron swelling zone by cns cohesive.
One of the methods for constructing embankments on expansive soils is to lay a cns nonswelling clay layer at the base of the. Characteristics of cohesive soils stabilized by cement kiln dust athraa m. The problem of heave or uplift of foundations caused by expansive soils is one of tension developed in the soil due to swelling. In 1978, mr katti had proposed concept of using cohesive non swelling layer to reduce effect of swelling. Scour in cohesive soils federal highway administration. Inhibition effect of swelling characteristics of expansive soil using. There are a number of methods available to stabilize expansive soil such as soil replacement, sand cushion, cohesive non swelling layer, mechanical, chemical and thermal stabilization etc.
Laying cns cohesive non swelling layer on expansive soil is studied. As already mentioned, the water content has an important influence on the behaviour of a cohesive soil. Determining of thickness of cohesive non swelling soil. Soil shrinkage characteristics in swelling soils 475 types of soil swelling when a dry soil wets, during the first stage it undergoes three dimensional 3d volumetric expansions, because its desiccation cracks are still opened figure 6. The basic physical and chemical properties of expansive and non swelling soils are presented in table 1. Certain studies indicated that a cohesive non swelling soil cns layer may prove to be effective in resisting the swelling and swelling pressure of underlying expansive soil. The soil behaves like a soft soil under wetsaturated condition. Cns cohesive nonswelling soil mechanics acronymfinder. Nondimension chart to determine the thickness of cns soil to. The parameters used to describe the response of cohesive soils to stress or pressure are the consistency or atterberg limits shrinking, plastic and liquid limit and the plasticity index, respectively. Cns layer creates an environment similar to that around 1 m deep in an expansive soil with equivalent cohesion to counteract heave. Sand type not clay type soil non cohesive soil is any freerunning type of soil, such as gravel or sand, whose strength depends on friction between soil particles.
Chemical processes such as mixing with cement, fly ash, lime, lime byproducts and blends of any one of these materials can be used to alter soil properties such as strength, compressibility, hydraulic conductivity, swelling potential and volume change properties. Cns stands for cohesive non swelling soil mechanics. Inhibition effect of swelling characteristics of expansive. Oct 23, 2016 cohesive non swelling soils cns with a suitable thickness depending up on the swelling characteristics of the expansive soils. The expansive soils are mixed with cohesive non swelling soil which is coarser than 425p as it will have influence on liquid limit of the soil. What is the percentage of water with respect to soil. This cohesive force helps to counter heave in soil beneath, even though the soil within the zone itself swells. Pdf physical properties play an important role in determining soils suitability for agricultural, environmental and engineering uses. What is the difference between cohesive and cohesionless soil. Cohesive nonswelling soil cns cushion technology is widely used to solve swelling deformation problems in expansive soil areas.
The cation concentration and swelling characteristics of these soil samples were measured. College of engineering, tirupati, andhra pradesh, india. Standard test methods for onedimensional swell or collapse of cohesive soils1 this standard is issued under the. This section discusses the relationships among these factors. Soil testing lab, laboratory services geotesting geocomp. However, the swelling inhibition mechanism is still not fully. The expansive soil used in this study was sampled in nanning, guangxi zhuang autonomous region, china. Investigation on engineering properties of soilmixtures. Interpretation of rice husk ash on geotechnical properties of cohesive soil tan sarkar. This report summarizes a study through which an erosion. M, gou t ham sarang, c il n rav s nkar,laboratory investigation on black cotton soil stabilized with non. Mechanical stabilization of soil without altering chemical properties includes controlled compaction 2, prewetting 3, mixing with sand 2, 4, use of cohesive non swelling soil 5, and reinforcing the soil using geosynthetics 6, 7. Narowal nandipur soil characteristics property soil soil cns for. Indeed, if different clays erode at different rates, then the erosion function and therefore its parameters should be functions of the soil properties.
The soil mixtures are prepared by mixing s1, s2, and s3 soils with 0%, 15%, 20%, and 25%, 30%, 35% of s4 soil. Finite element modeling of swelling soil pressures using. Cohesive non swelling soil cns cushion technology is widely used to solve swelling deformation problems in expansive soil areas. Standard test methods for onedimensional swell or collapse. Determining of thickness of cohesive non swelling soil layer. Gtxs fully equipped laboratories perform more than 100 different soils tests to determine physical properties. Stabilisation of rice husk ash for use as cushion below. Innovative techniques in road and rail construction on. Cohesive soil does not crumble, can be excavated with vertical sideslopes, and is plastic when moist. This cns is introduced between expansive soil mass and the lining material to counter act the effect of swelling press. Various tests are performed on the expansive soil to determine its swelling pressure test, tri. To overcome this limitation, which is thought to be due to the non cohesiveness of the. Variable cohesion model for soil shear strength evaluation.
First it is pretty intuitive that the more energy applied to the soil during compaction the more dense you will make it. To investigate the effects of adding cohesive nonswelling soil cns on expansive it. In areas with very less probability of seismic activities, vibratory ground improvement can reduce the potential for liquefaction and ground deformation due to lateral spreading. The idea clicked in the year 1967 and the cohesive nonswelling soil cns.
1315 679 1280 1117 136 425 1067 76 1122 1643 618 295 1042 1231 393 122 878 1125 237 1604 1499 1235 297 1515 430 1128 890 783 583 915 1215 448 710 1057 1092